Various attempts to fabricate practical and economical thermophotovoltaic (TPV) power generators have been reported over the years. However, generator designs based on the use of silicon photovoltaic cells have been unsuccessful because of a requirement for very high temperature emitters (T&gt;2300K). Without very high temperature emitters, TPV systems based on silicon cells are both inefficient and operate at low power densities. Selective emitters based on rare earth oxides have been described (M. K. Goldstein, U.S. Pat. No. 4,976,606) which improve efficiencies but still suffer from low power densities at practical emitter temperatures. Low power density generators are not economical for large volume energy production.
In 1989, L. M. Fraas et. al. described a new GaSb photovoltaic cell sensitive in the infrared (IR) out to 1.8 microns. Later in 1989, M. D. Morgan, W. E. Horne, and A. C. Day proposed using GaSb cells in combination with a radioisotope thermal source for space electric power and in 1991, O. L. Doellner proposed using GaSb cells looking at jet engine plumes to replace alternators on jet aircraft. Finally in 1992, A. P. Fraas and R. M. Fraas submitted U.S. patent application No. 07/906,452, now U.S. Pat. No. 5,312,521, and application Ser. No. 047,477, describing a small quiet natural gas fired TPV generator using GaInSb cells.
Now realizing that a variety of TPV generator designs are possible incorporating GaSb cells, we have invented a generic interchangeable TPV receiver assembly that can be incorporated in a variety of large or small generators. Our TPV receiver assembly incorporates series connected TPV cells in a line on a thermally conductive circuit carrier which is directly bonded to a parallel cooling channel. The cooling channel also supports and cools parallel mirror elements which concentrate infrared energy efficiently to the series connected cell string. The cell interconnections are hidden under the mirror elements. The mirror elements, cooling channel, circuit carrier, and series connected cell string together form a linear TPV receiver assembly with + and - terminals on either end. Identical receiver assemblies can be packed side by side, each facing the emitter in a large variety of TPV generator configurations.
No such TPV receiver assemblies have been described previously in the literature. The Doellner configuration is specific to a jet engine. Furthermore, the receiver descriptions found in Morgan et. al. and Goldstein et. al. both assume the cells are tightly packed in an array located very close to the emitter without IR concentrating elements. In the case that there is air between the emitter and the receiver assembly as would probably be the case for economical consumer products, it is desirable to have a significant spacing between the emitter and the IR TPV receiver to minimize heat transfer by nonradiative means. In this case, it is desirable to use IR concentrating elements to restore the IR power density at the TPV cell location back to the level available at the surface of the emitter. The use of IR concentrating elements will therefore minimize the amount of expensive single crystal TPV cell material required.
In summary, there is a need for a TPV receiver assembly design which provides for series connecting circuitry, high power conversion efficiency, high infrared power densities, good thermal management, modularity, and simplicity. Our receiver design accomplishes all of these goals.